The invention relates to an electric power distribution switch and an auxiliary biasing mechanism therefor. One type of electric power distribution switch includes one or two sets of three stationary, fixed contacts and a rocker arm assembly which includes a set of three movable contacts mounted on a rocker arm. The rocker arm assembly rotates to make and break contact between the movable contacts and the fixed contacts. A spring-loaded operator rotates the rocker arm assembly to provide snap-action opening and closing of the switch in response to manual rotation of a handle. An example of a switch of this type which has proven successful in commercial use is described in commonly assigned U.S. Pat. No. 4,467,161, which is incorporated herein by reference. An operator for this type of switch is described in commonly assigned U.S. Pat. No. 3,403,565, which is also incorporated herein by reference.
When an electric current flows through a set of movable contacts in close proximity to or in contact with a set of fixed contacts, electrically generated repulsive forces, sometimes known as "blow-out" forces, urge the respective sets of contacts apart. Such forces are proportional to the square of the current flowing through the contacts. The forces are relatively low for normal current conditions, but become significant when the switch is being closed into a fault condition. When the switch is closed into a fault, arcing between the contacts may commence when the contacts are a small distance apart, and the resultant repulsive forces oppose the closing forces provided by the operator. The ability of the switch to close into a fault may be limited by the magnitude of the repulsive forces which can be overcome when closing the switch. An object of the invention is to provide an electric power distribution switch having increased capacity to overcome such repulsive forces.